Intrathecal catheter

ABSTRACT

An intrathecal catheter for delivering fluid to, or withdrawing fluid from, the cerebrospinal fluid compartment of a patient, includes a proximal end and a distal portion. The distal portion has an outer diameter of about 1 mm or less, a bending stiffness of about 0.002 pounds per square inch or less, and a distal end. A delivery region is located between the proximal end and the distal end, and a lumen extends from the proximal end to the delivery region. The catheter may further include a coiled structure region to prevent dislodgement of the catheter from a tissue in which the coiled structure is implanted, for example the cisterna magna. The catheter may also include tines to anchor portions of the catheter, for example to a portion of the spinal canal.

RELATED APPLICATIONS

This Application claims the benefit of Provisional Application Ser. No.60/868,901, filed Dec. 6, 2006, and of Provisional Application Ser. No.60/868,904, filed Dec. 6, 2006, which applications are herebyincorporated herein by reference in their respective entireties to theextent that they do not conflict with the present disclosure.

FIELD

The present disclosure relates, inter alia, to implantable medicalcatheters, and particularly to intrathecal catheters.

BACKGROUND

A variety of catheters are available for delivering therapeutic agentsto patients. Configurations of the catheters vary according to the usefor which they are intended. For example, intravascular catheters mayinclude a coiled region that presses against the vasculature to hold thecatheter in place during use. The use of tines has also been employedfor purposes of anchoring a catheter relative to a tissue location. Thematerials and properties of the catheters may be selected to becompatible with the therapeutic agent being delivered and the tissueinto which the catheter is to be implanted.

Recently, therapies have been proposed for delivering therapeutic agentsto the cisterna magna. However, to date, no catheters have beendescribed that would be suitable for such delivery, particular for longterm delivery; e.g., as typically associated with implantable infusiondevices.

SUMMARY

The present disclosure describes catheters and kits and systems suitablefor delivering therapeutic agents to the cisterna magna, particularlywhen the catheters are advanced rostrally through the spinal canal tothe cisterna magna.

In an embodiment, a catheter includes a proximal end and a distalportion. The distal portion has an outer diameter of about 1 mm or less,a bending stiffness of between about 0.00005 pound inch squared(1.4×10⁻⁸ kg-meter squared) to about 0.002 pound inch squared (5.8×10⁻⁷kg-meter squared), and a distal end. A delivery region is locatedbetween the proximal end and the distal end, and a lumen extends fromthe proximal end to the delivery region. The material forming the distalportion of the catheter imparts a sufficient hoop strength such that thelumen resists collapsing when implanted in the cerebrospinal fluidcompartment of a subject. The catheter may further include a coiledstructure region to prevent dislodgement of the catheter from a tissuein which the coiled structure is implanted, for example the cisternamagna, or to allow for growth of the patient in height when implanted ina young patient. The catheter may also include tines to anchor portionsof the catheter, for example to a portion of the spinal canal.

In an embodiment, a catheter includes a proximal end and a distalportion. The distal portion includes a delivery region and a coiledstructure region. A lumen extends from the proximal end to the deliveryregion. One or more tines are located on the catheter proximal to thedelivery region and the coiled structure region.

The catheters described herein provide one or more advantages overexisting catheters. For example, in various embodiments, the cathetersinclude a flexible distal end portion that can reduce or prevent tissuedamage when being advanced through delicate tissue such as the cisternamagna. In various embodiments, the catheters are configured to provideanchoring within the cisterna magna or spinal canal to preventdislodgement of a delivery region of the catheter from the cisternamagna. These and other advantages will become evident upon reading thedisclosure that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic longitudinal cross sectional view of arepresentative catheter.

FIG. 2A is schematic side view of a representative catheter.

FIG. 2B is a schematic exploded side view of a representative catheter,adaptor, and second catheter.

FIG. 3 is a schematic longitudinal cross section of a distal portion ofa representative catheter.

FIG. 4 is a schematic longitudinal cross section of a representativedistal portion of a catheter with a stylet inserted into a lumen of thecatheter.

FIG. 5 is a schematic longitudinal cross section of a stylet insertedinto a lumen of a catheter.

FIG. 6 is a schematic longitudinal cross section of a portion of acatheter including a visualization marker.

FIG. 7 is a schematic longitudinal cross section of a representativedistal portion of a catheter with a stylet inserted into a lumen of thecatheter.

FIG. 8 is a schematic perspective view of a coiled structure region of arepresentative catheter.

FIG. 9 is a schematic longitudinal section of a portion of arepresentative catheter having a coiled structure region and tines.

FIG. 10 is a schematic side view of an implantable infusion device withan attached catheter.

FIG. 11 is a schematic view of an infusion device and associatedcatheter implanted in a patient.

The drawings are not necessarily to scale. Like numbers used in thefigures refer to like components, steps and the like. However, it willbe understood that the use of a number to refer to a component in agiven figure is not intended to limit the component in another figurelabeled with the same number.

DETAILED DESCRIPTION

In the following detailed description, reference is made to theaccompanying drawings that form a part hereof, and in which are shown byway of illustration several specific embodiments of devices, kits,systems and methods. It is to be understood that other embodiments arecontemplated and may be made without departing from the scope or spiritof the present invention. The following detailed description, therefore,is not to be taken in a limiting sense.

Devices and methods for delivering large molecules to the centralnervous system (CNS) are discussed. The devices and methods describedallow for less invasive and more effective procedures to be employed fordelivering medications comprised of drugs, small molecules, or largemolecules to the brain.

Definitions

All scientific and technical terms used herein have meanings commonlyused in the art unless otherwise specified. The definitions providedherein are to facilitate understanding of certain terms used frequentlyherein and are not meant to limit the scope of the present disclosure.

As used herein, “the cerebrospinal fluid compartment” of a subject meansthe space within the central nervous system within the anatomy of thesubject that is filled with cerebrospinal fluid. The cerebrospinal fluidcompartment comprises the cisterna magna, the lateral ventricles, thethird ventricle, the fourth ventricle, the foramen of Magendie, theforamen of Monro, the formina of Luschka, the cerebral aquaduct, thesubarachnoid space surrounding the brain and the spinal cord, the duralvenous sinuses, spaces surrounding the cranial nerves, and other spacesof the central nervous system containing cerebrospinal fluid.

As used herein, “visualization marker” means material that is visible bysurgical navigation instrumentation. A marker may be a discrete band ormay be in any other suitable form for visualization purposes. Markersmay comprise radiopaque material, such as platinum, tungsten, gold oriridium. Markers may be incorporated into catheter material or may beaffixed to a portion of a catheter.

As used herein, “subject” means an animal into which a catheter or aportion thereof may be implanted and includes mammals, such as humans.

As used herein, “comprising”, “including”, and the like are used in anopen-ended fashion, and thus should be interpreted to mean “including,but not limited to . . . ”

As used in this specification and the appended claims, the singularforms “a”, “an”, and “the” encompass embodiments having pluralreferents, unless the content clearly dictates otherwise. As used inthis specification and the appended claims, the term “or” is generallyemployed in its sense including “and/or” unless the content clearlydictates otherwise.

Abbreviations of units of measurements as used herein are abbreviationscommonly used in the art unless otherwise specified. For example, “mm”means millimeter, “cm” means centimeter, and “kg” means kilogram.

Described herein are catheters having properties that are useful fordelivering fluid to or withdrawing fluid from the cisterna magna of asubject. However, it will be understood that the properties of thecatheters may be useful for delivering or withdrawing fluid to otherareas of a subject.

Referring to FIG. 1, catheter 100 has a proximal end 10 and a distalportion 20. As used herein, “proximal” refers to the portion of thecatheter closer to a fluid delivery or withdrawal device and “distal”refers to the portion of the catheter further from the fluid delivery orwithdrawal device when in use. Distal portion 20 comprises a distal end30 and a delivery region 40. Catheter 100 comprises a lumen 50 extendingfrom proximal end 10 to delivery region 40. Delivery region 40 in FIG. 1is depicted as a side hole. However, it will be understood that deliveryregion 40 may be one or more side holes, one or more porous regions (notshown) that extend around or substantially around a portion of distalportion 20 of catheter 100, an opening (not shown) at distal end 30, orthe like. It may be desirable in many circumstances to have more thanone opening for fluid to be delivered or withdrawn in case one or moreopenings becomes clogged during or following implantation of catheter100.

As shown in FIG. 1, distal portion 20 of catheter 100 has an outerdiameter (o.d.). In various embodiments o.d. of distal portion 20 isless than about 1 mm. For example, o.d. may be less than 0.75 mm or lessthan 0.62 mm. Catheter 100 having a distal portion 20 with an o.d. ofless than about 1 mm may tend to be too limp to be pushed largedistances within a subject's body, such as from the intrathecal lumbarregion to the cisterna magna, particularly if made from certainpolymeric materials. However, such a limp catheter 100 tends to reducethe chance of damaging tissue into which catheter 100 is inserted, suchas the intrathecal space. Accordingly, it may be desirable to employ astylet 200 (see, e.g., FIG. 3) to direct catheter 100 to the appropriatelocation within the subject. Of course, a long introducer (not shown) orguiding catheter (not shown) may be used to provide a guide throughwhich the thinner catheter 100 could be pushed without bending or goingoff course.

In various embodiments, distal portion 20 of catheter 100 has a bendingstiffness low enough to avoid significant damage to tissue, such as thearachnoid membrane, as distal portion 20 of catheter 100 is advancedthrough the tissue. Bending stiffness can be measured using thefollowing formula:

Mρ=E I,

-   -   where M=bending moment;    -   ρ=radius of curvature;    -   E=Young's Modulus for the material selected; and    -   I=moment of inertia for the beam.

The moment of inertia for simple cross sections are readily available tothose skilled in the art, e.g., through textbooks or handbooks.Otherwise, the moment of interia can be calculated as follows:

$I_{solidcylinder} = {\frac{\pi}{64}({OD})^{4}}$

where OD is the outside diameter of the stylet, or

$I_{hollowtube} = {\frac{\pi}{64}( {({OD})^{4} - ({ID})^{4}} )}$

where OD is the outside diameter of the cannula and ID is the insidediameter.

In various embodiments, the bending stiffness of distal portion 20 ofcatheter 100 may be about 0.002 pound-inch squared (5.8×10⁻⁷ kg-metersquared) or less, such as about 0.001 pound-inch squared (2.9×10⁻⁷kg-meter squared) or less, to prevent significant damage to delicatetissue, such as the tissue surrounding the spinal canal or the cisternamagna, as distal portion 20 is being advanced through the tissue. Innumerous embodiments, the bending stiffness of distal portion 20 ofcatheter 100 is between about 0.002 pound-inch squared (5.8×10⁻⁷kg-meter squared) and 0.00005 pound-inch squared (1.4×10⁻⁸ kg-metersquared). Of course a catheter having such a low bending stiffness maybe difficult to advance through the spinal canal. Accordingly, it may bedesirable to use a stylet 200 (see, e.g., FIG. 3) to assist in directingcatheter 100 to the appropriate location within the subject. Distalportion 20 of catheter 100 and stylet 200 disposed within lumen 50 ofdistal portion 20 of catheter 100, in combination, should besufficiently stiff to advance distal portion 20 of catheter 100 throughtissue. If distal portion 20 of catheter 100 is to be advanced throughthe spinal canal, distal portion 20 of catheter 100 and stylet 200disposed within lumen 50 of distal portion 20 of catheter 100, incombination, should have a bending stiffness of about 0.01 pounds inchsquared (2.9×10⁻⁶ kg meter squared) or greater.

It will be desirable for distal portion 20 of catheter 100 to havesufficient hoop strength to resist collapse of the lumen 50 when thecatheter 100 is implanted in the cerebrospinal fluid compartment of thesubject. Examples of material that can impart sufficient hoop strengthat the diameters discussed above include polypropylene and polyethylene.

Distal portion 20 of catheter 100 may vary in length to achieve adesired effect; e.g., advancement into the cisterna magna from a lumbarinsertion. For example, the distal portion 20 may be about 40 cm orlonger, about 50 cm or longer, about 60 cm or longer, about 70 cm orlonger, about 80 cm or longer, about 90 cm or longer, or about 100 cm orlonger. The longer the distal portion 20 of catheter 100, which may havea small outer diameter, the less likely that catheter 100 will damagetissue as catheter 100 is advanced within a subject, and thus the morelikely that it may be advanced extended distances in delicate tissue. Inaddition, due to a small outer diameter, distal portion 20 of catheter100 may have a small inner diameter, which will permit fine control offluid to be delivered. However, it should be noted that due toresistance to fluid flow associated with smaller inner diameter,catheter 100 preferably has a sufficiently large inner diameter topermit bolus delivery of fluid through the catheter 100. While it willbe understood that resistance may vary from solution to solution orcatheter to catheter, it may be difficult to deliver substantial bolusamounts if the inner diameter of the catheter (i.e., the lumen diameter)is less than about 0.127 mm.

In various embodiments, proximal end 10 of catheter 100 is configured tobe coupled to an infusion device 300 (see, e.g., FIG. 10). Proximal end10 of catheter 100 may be coupled to infusion device 300 using any knownor future developed mechanism. In embodiments wherein the outer diameterof distal portion 20 of catheter 100 is small, catheter 100 may includea tapered portion 500 between proximal end 10 and distal end 30 toprovide a proximal end 10 with a larger outer diameter (see, e.g., FIG.2A) to facilitate coupling of the catheter 100 to the infusion device300. As shown in FIG. 2B, an adaptor 600 may be used to fluidly couplethe lumen of the catheter 100 to a second catheter 700, which may thenbe coupled to the infusion device. Of course, the adaptor 600 may beconfigured to couple catheter 100 directly to the infusion device.

Referring to FIG. 3 and in accordance with various embodiments, thelumen 50 of the catheter is configured to slidably receive a stylet 200.In the depicted embodiment, distal portion 20 of catheter 100 has a sidehole delivery region 40. Disposed within lumen 50 is a stylet 200including a distal end 210. As used herein, “stylet” means an elongateddevice capable of being inserted into lumen 50 of catheter 100 andassisting the movement of distal portion 20 of catheter 100 to a desiredlocation in a subject, and includes a guidewire and the like. Stylet 200may be used to push distal portion 20 of catheter 100 or may be used toimpart stiffness to distal portion 20 of catheter 100 to allow catheter100 to be positioned within a subject, e.g., where the stylet 200 andthe catheter 100 are advanced together. It will generally be desirablefor excess catheter material to extend beyond distal end 210 of stylet200 to allow material softer than stylet 200 to be exposed to tissue asdistal portion 20 of catheter 100 and stylet 200 are advanced. Any wayto ensure that distal end 210 of stylet 200 does not extend beyonddistal end 30 of catheter 100 may be used. As shown in FIG. 3, acatheter 100 having a closed distal end 30 may be one way of preventingstylet 200 from extending beyond distal end 30 of catheter 100.Alternatively, catheter may be squeezed, e.g. by a user's fingers, toapply sufficient pressure to prevent relative longitudinal movement ofstylet 200 to distal portion 20 of catheter 100 as distal portion 20 ofcatheter 100 and stylet 200 are advanced together.

FIG. 4 depicts an embodiment of a catheter 100 having a feature 70 toprevent accidental extension of stylet 200 beyond distal end 30 ofcatheter 100 or accidental protrusion of stylet 200 through side holedelivery region 40. As shown in FIG. 4, excess catheter material 80 maybe present between the feature 70 and distal end 30 of catheter 100 toallow a material softer than stylet 200 to be exposed to tissue ascatheter 100 and stylet 200 are being advanced. In the depictedembodiment, feature 70 is configured to receive distal end 210 of stylet200, which may be useful in circumstances where it is desirable to usestylet 200 to push distal portion 20 of catheter 100.

Referring to FIG. 5, an alternative embodiment for preventing accidentalextension of stylet 200 beyond distal end 30 of catheter 100 is shown.As shown in FIG. 5, stylet 200 may include a stop 230 or handle at theproximal region of stylet 200 that prevents distal end 210 of stylet 200from extending beyond distal end 30 of catheter 100 during use. Invarious embodiments, the length of stylet 200 from stop 230 to distalend 210 of stylet 200 is less that the length of catheter 100 (ifstraightened) from proximal end 10 to distal end 30. In variousembodiments, the length of stylet 200 from stop 230 to distal end 210 ofstylet 200 is less than the length of catheter 100 (if straightened)from proximal end 10 to an opening of delivery region 40. It may bedesirable for the length of stylet 200 to be shorter than the length ofcatheter 100 by an amount to allow sufficient excess catheter materialto extend beyond distal end 210 of stylet 200 while catheter 200 isbeing advanced within a subject. The position of stop 230 on stylet 20may be fixed or adjustable to the desired length.

Generally, stop 230 is configured to grippingly engage an outer surfaceof stylet 20 and to engage the proximal end of the catheter. If stop 230is moveable along stylet 20, the stop 230 may exist in an open state anda closed or engaged state. In the open state the stop 230 is moveable.In the closed state the stop 230 is fixed relative to the stylet 20. Invarious embodiments, the stop 230 is actuatable between the open andclosed states. Suitable actuatable mechanisms for stops 230 are wellknown and include set screws, squeezable handles or the like.

In various embodiments, kits including a catheter 100 as describedherein and a stylet 200 are provided. Any suitable stylet 200, such as astylet as described above, may be included in the kit. In numerousembodiments, the catheter 100 and the stylet 200 of the kit are providedin a single package.

Referring to FIG. 6, a cross-sectional representation of an embodimentof distal portion 20 of catheter 100 is shown. As shown in FIG. 6, avisualization marker 60 may be disposed in or about a portion ofcatheter 100 in proximity to delivery region 40 to serve as a proxy foridentification of the location of the delivery region. Visualizationmarker 60 may be in the form of a band as shown in FIG. 6, or may takeany other suitable form to serve as a means for localizing the placementof delivery region 40 by surgical navigation visualization techniques.

As shown in FIG. 7, stylet 200 may comprise visualization marker 220 ator near distal end 210 to further enhance visualization of navigationand placement of delivery region 40 of catheter 100. Visualizationmarker 220 may be in the form of a band as shown in FIG. 7, or may takeany other suitable form to serve as a means for localizing distal end210 of stylet 200, which may serve as a proxy for placement of deliveryregion 40 by surgical navigation visualization techniques. Visualizationmarker 220 may also be used to verify that distal end 210 of stylet 200is not extended beyond distal end 30 of catheter 100 (as indicated byvisualization marker 60 of catheter 100) during placement of catheter100.

In various embodiments, at least a portion of distal portion 20 ofcatheter 100 comprises a coiled structure 90 when relaxed, as shown inFIG. 8. A “coiled structure”, as used herein, may have one or more loopsor other nonlinear portions (e.g., a sigma structure) that may serve toanchor distal portion 20 of catheter 100 within a location of the body,such as the cisterna magna. Such a coiled structure 90 may be desirablein situations where catheter 100 is likely to undergo a strain due tobody movements of the subject. For example, if catheter 100 isintroduced into the intrathecal space of the spinal canal through alumbar puncture and advanced rostrally so that distal portion 20 ofcatheter 100 is located in the cisterna magna, movement of the subject'shead or neck may tend to dislodge distal portion 20 of catheter 100 fromthe cisterna magna. As such, a coiled structure portion 90 of distalportion 20 of catheter 100 may serve to provide strain relief to preventpulling or dislodging of distal portion 20 of catheter 100. Such acoiled structure portion 90 may also be beneficial when catheter 100 isimplanted in an infant or child, where growth of the spine may otherwisetend to dislodge distal portion 20 of catheter 100 from its desiredlocation, e.g. the cisterna magna. The coiled structure portion 90 ofdistal portion 20 of catheter 100 is sufficiently pliable to bestraightened when a stylet 200 is inserted into lumen 50 of catheter 100and extended through coiled portion 90 of catheter 100. In addition toproviding strain relief, coiled structure portion 90 may also serve toanchor distal portion 20 of catheter 100 in place.

It may be desirable to include one or more visualization markers 60 (notshown in FIG. 8) on coiled structure portion 90 to verify that thecoiled structure portion 90 has been appropriately implanted ornavigated. Alternatively, it may be desirable to incorporate radiopaquematerial into catheter material of coiled structure portion 90 to allowfor visualization during or after implant.

Referring to FIG. 9, a representation of an embodiment of distal portion20 of catheter 100 as it may appear implanted in a subject is shown.Distal portion 20, which may be implanted in the cisterna magna,comprises a coiled structure portion 90 comprising distal end 30 ofcatheter 100. Included in the depicted coiled structure portion 90 aredelivery regions 40 and visualization marker 60. Placement of deliveryregion 40 within the coiled structure region 90 may serve to keepdelivery region located away from a tissue of the subject, rather thanallowing the delivery region to contact or be in close proximity totissue of the subject when implanted. Such a configuration may bedesirable to prevent granulomas that may occur with certainintrathecally delivered drugs.

While not shown, it will be understood that it may be desirable forcoiled structure region 90 to comprise more than one visualizationmarker 60 or to have a visualization marker 60 extend over a substantialportion of coiled structure region 90, e.g., by incorporating aradiopaque material into the catheter at coiled structure region 90.

Distal portion 20 of catheter 100 may comprise one or more tines 110 toassist in anchoring distal portion 20, and more particularly deliveryregion 40. Tines 110 may be located at any location along catheter 100that may result in anchoring the catheter 100 or reduce movement ofdelivery region 40. As shown in FIG. 9, tines 110 may be located furtherfrom distal end 30 of catheter 100 than coiled structure portion 90(e.g., the tines are located proximal to the coiled structure region),e.g. at a location of catheter 100 to be implanted within a spinalcanal. Also shown in FIG. 9, is that excess 120 catheter 100 may beplaced in the spinal canal to provide slack to allow for growth of asubject, such as a child. Tines 110 may be made of any material that canprovide sufficient anchoring to inhibit movement of the catheterrelative to the tissue in which the tines 110 are anchoring thecatheter. In the depicted embodiment, the tines 110 are oriented toallow rostral advancement of the catheter in the spinal canal but toinhibit caudal withdrawal or movement of the distal portion 20 of thecatheter. However, the tines 110 may be retractable, as is known in theart, to prevent damage to the spinal canal upon withdrawal of thecatheter. One example of retractable tines is presented in U.S. Pat. No.6,695,861.

Referring to FIG. 10, catheter 100 is shown operably coupled to aninfusion device 300. Catheter 100 may be connected to infusion device300 via catheter connector 330. Infusion device 300 shown in FIG. 10comprises a refill port 310 in fluid communication with a reservoir (notshown) for housing a fluid to be infused to into a subject via catheter100, which is in fluid communication with reservoir. Infusion device 300as depicted in FIG. 10 also comprises an injection port 320, which is influid communication with catheter. Fluid, e.g. fluid containingtherapeutic agent, may be injected into injection port 320, e.g. todeliver a bolus of therapeutic agent. Examples of infusion devices 300having injection ports 310 in fluid communication with reservoirs andhaving injection ports 320 are Medtronic, Inc.'s SynchroMed® series ofinfusion devices. While not shown, it will be understood that infusiondevice 300 may be any device that is capable of delivering a fluidthrough catheter 100, such as a syringe, a device having a pump (e.g.,osmotic, peristaltic, piston, etc.), an access port, and the like.

Referring to FIG. 11, a programmable infusion device 300, such asMedtronic, Inc.'s SynchroMed® series of infusion devices, is shownimplanted in a human. As shown in FIG. 11, distal end 30 of catheter 100may be inserted into a subject's spinal canal through a lumbar punctureand advanced rostrally through the spinal canal to a desired location.Proximal end 10 of catheter 100 is coupled to infusion device 300, whichis typically implanted in the subject at a subcutaneous location.Infusion device 300 comprises a receiver 42 (or transmitter) which iscapable of telemetric communication (or any other suitable form ofcommunication) with programmer 400. Programmer 400 may communicate withan implantable infusion device 300 to adjust the amount of therapeuticagent delivered. Communication may be unidirectional; e.g., programmer400 to infusion device 300, or bi-directional. Generally, programmer 400is placed over skin in an area where infusion device 300 is implanted tocommunicate with device 300. While not shown, it will be understood thatone or more sensors may be operably coupled to infusion device 300 toalter the rate at which therapeutic agent is delivered. Programmableinfusion devices are particularly amenable to alteration of infusionrate via sensors. One advantage of the use of programmable infusiondevices over non-programmable devices is that the rate of delivery oftherapeutic agent from infusion device 300 may be altered as a patient'scondition warrants or to optimize therapeutic efficacy.

In general, it will be understood that catheter 100, or portionsthereof, may be made of any material that is compatible with a subjectin which catheter 100 is implanted and with fluid to be deliveredthrough catheter 100. Material selection for the catheter may be basedon mechanical properties of the tubing, drug stability (changes in thedrug due to the catheter material), drug compatibility (changes in thecatheter material due to the drug), biostability (changes in thematerial due to the in vivo environment), biocompatibility (effects ofthe material on the patient), and the like. Generally catheter 100 orportions thereof will be made of polymeric material such as silicone,polyurethane, polyethylene, polypropylene, or the like. If polypeptidesare to be delivered via catheter 100, it may be desirable to usepolymeric materials other than silicone, as the polypeptide may adhereto or be absorbed into the silicone or may be degraded.

Thus, embodiments of the INTRATHECAL CATHETER are disclosed. One skilledin the art will appreciate that the present invention can be practicedwith embodiments other than those disclosed. The disclosed embodimentsare presented for purposes of illustration and not limitation, and thepresent invention is limited only by the claims that follow.

1. An intrathecal catheter for delivering fluid to, or withdrawing fluidfrom, the cerebrospinal fluid compartment of a subject, the cathetercomprising: a proximal end; a distal portion having an outer diameter ofabout 1 mm or less, a bending stiffness of between about 0.0005pounds-inch squared to about 0.002 pounds-inch squared, and a distalend; a delivery region located between the proximal end and the distalend; and a lumen extending from the proximal end to the delivery region,wherein the material forming the distal portion of the catheter hassufficient hoop strength to resist collapsing of the lumen whenimplanted in the cerebrospinal fluid compartment.
 2. The catheter ofclaim 1, further comprising a visualization marker disposed in or aboutthe distal portion in proximity to the delivery region.
 3. The catheterof claim 1, wherein the length of the catheter from the proximal end tothe delivery region is about 40 cm or more.
 4. The catheter of claim 1,wherein the distal portion further comprises a coiled structure region.5. The catheter of claim 4, wherein the delivery region located in thecoiled structure region.
 6. The catheter of claim 4, wherein the coiledstructure region is capable of being straightened upon insertion of astylet into the lumen of the catheter.
 7. The catheter of claim 1,wherein the catheter is formed from a polymeric material.
 8. Thecatheter of claim 1, wherein the catheter is formed from a materialcomprising polypropylene.
 9. The catheter of claim 1, wherein thecatheter is formed from a material comprising polyethylene.
 10. A kitcomprising: a catheter according to claim 1; and a stylet having aproximal end, and a distal portion, the distal portion comprising adistal tip and being configured to be slidably disposable in the lumenof the catheter.
 11. The kit of claim 10, further comprising a stopmechanism configured to grippingly engage an outer surface of the styletand to engage the proximal end of the catheter as the stylet is insertedinto the lumen of the catheter to prevent the stylet from being advancedinto the lumen beyond a point where the distal tip of the stylet extendsthrough the lumen and beyond the delivery region of the catheter. 12.The kit of claim 11, wherein the stop mechanism is capable of beingactuated between an open and a closed state, wherein the stop mechanismin the open state is moveable relative to stylet and wherein the stopmechanism in the closed state is configured to grippingly engage thestylet.
 13. The kit of claim 10, further comprising a stop mechanismconfigured to grippingly engage an outer surface of the stylet and toengage the proximal end of the catheter as the stylet is inserted intothe lumen of the catheter, wherein the length of stylet from location ofstop mechanism to distal tip is less than length of the lumen fromproximal end of catheter to delivery region.
 14. A system comprising: acatheter according to claim 1; and an implantable infusion deviceoperably couplable to the catheter such that fluid is deliverable fromthe device to a patient via the delivery region of the catheter when thesystem is implanted in the patient.
 15. A catheter comprising: aproximal end; a distal portion including a delivery region and a coiledstructure region; one or more tines located proximal to the deliveryregion and the coiled structure region; and a lumen extending from theproximal end to the delivery region.
 16. The catheter of claim 15,wherein the delivery region is located within the coiled structureregion.
 17. The catheter of claim 15, wherein the delivery region islocated distal to the coiled structure region.
 18. The catheter of claim15, wherein the coiled structure region is capable of being straightenedupon insertion of a stylet into the lumen of the catheter.
 19. A systemcomprising: a catheter according to claim 15; and an implantableinfusion device operably couplable to the catheter such that fluid isdeliverable from the device to a patient via the delivery region of thecatheter when the system is implanted in the patient.